Touchscreen displays are “electronic visual display[s] that can detect the presence and location of a touch within the display area.” (http://en.wikipedia.org/wiki/Touchscreen). They have become increasingly prominent in modern electronics as they provide for a highly effective and intuitive means of interacting with a device.
Current touchscreen displays utilize any one of several technologies to perceive contact—those technologies can be broadly classified as infrared optical technologies and non-infrared-optical technologies. Touchscreen displays that rely on infrared optical technologies typically operate by projecting a plurality of distinct light beams so as to form a Cartesian-type grid above the surface of a display. Each light beam is typically received at the other end of the display surface by a corresponding ‘receiver.’ When the screen is touched or otherwise contacted, the lines of site between specific light beams and their respective receivers may become obstructed. Thus, a location of contact may be determined based on which specific lines of sight are obstructed.
Typically, in accordance with this type of system, light-emitting diodes (“LEDs”) are used to project the light beams. LEDs are essentially semiconducting light sources. (http://en.wikipedia.org/wiki/Light-emitting_diode). Similarly, these light beams are typically received by photodiodes. Photodiodes are photodetectors that are capable of converting light into an electrical signal. (See e.g., http://en.wikipedia.org/wiki/Photodiode).
FIG. 1 illustrates a typical optics-based touchscreen display. Light beams are projected across the surface of the touchscreen display 101 via LEDs 102, and they are projected through perpendicular trajectories 104 and 106. Each of the light beams projected is received at the other end of the touchscreen display by a particular photodiode 108. The photodiodes 108 signal the reception of the incident light beams to an associated microprocessor 110. A member that contacts the surface of the display will intercept certain of the projected light beams. Thus, the microprocessor 110 can compute the location of contacting member by evaluating which of the photodiodes is not signaling the reception of incident light beams because of the obstructing contacting member.